Method of curing and treating tobacco



I ventilation.

being further treated.

ITE STATES PAT NT OFFICE.

ALFRED CHARLES BUENSOD, OF NEW YORK, N. Y.

METHOD OF CURING-AND TREATING TOBACCO.

No Drawing.

in curing barns, which vary greatly insizeand type. The smaller barns,which are made from 15 to 20"long and 10 to 20 wide, are mostlyconstructed from logs and are arranged for the use of high temperatures,suitable openings being provided for The larger barns, usually of frameconstruction, range in size from 120 to 2-00 long and 32' to -10 wide,are used mostly for natural air curing and are provided with a largenumber of ventilators. In many cases open fires or fines are used inthese barns to give a limited amount of heat.

The ventilating openings admit a good deal 'ofdaylight to the interiorof the barn, which is very undesirable.

The purpose of this curing treatment is that certain chemical changes inthecomposition of the leaf may take place to develop the desired color;regulate the temperature retaining capacity; control the texture, fireholding capacity and elasticity;

and producethe proper keeping qualities,

so that the tobacco will not decay before It is well known that alltobacco is subjected to aftertreatment for the purpose of developingcertain properties, such as aroma, flavor. etc. Although it is possibleto make this after treatment a continuation of the curing process, allthe changes in the tobacco described herein are those whiclr relate tothe curing process.-

The curing of tobacco comprises essentially the creation of suchchemical changes in certain compositions of the leaf which shall producethe lemon yellow, the orange,

the brown. the greenish brown, or the dark brown color desired invarious types of tobacco. together with the other properties.Chemically. the changes can be divided into two parts first, the periodin which the changes take place while the leaf is still alive and inwhich the green color is chemi- Spc cificat ion of Letters Patent.

e Application filed March 14, 1917. Serial No. 154,842.

cally changed to yellow; second, the period following the death of thecells, consisting mostly in oxidation of the various constituents of theleaf and producing the characteristic color of the tobacco.

The green tobacco leaf, after being harvested, always, contains certainenzyms which take an active part in the changes throughout the process,and, in the. period of cell starvation, they are greatly increased. The

formation of the color of the tobaccois entirely due to the oxidation ofthe cell substance through the medium .of an enzym. This oxidizingaction may take place at any time, either before or after the leaf hasturned yellow.

lVhen the green leaf is hung in 'an absolutely dark chamber, the actionof the rays of light and the moisture supply through the root systembeing cut ofl", a period of starvation 'sets in, and the reserve supplyof food stored in the leaf is consumed. It is necessary that tobacco becured in the absence ofthe direct or the indirect rays of sunlight inorder to extend the starving'process. This is so because plant life isdependent upon a food supply, a water supply, and the agencies of therays of sunlight for its development, andin curing, we deprive the plantof its source of water and its food supply and must also deprive it ofthe agencies of light. If light is present, although .the food and watersupply has been terminated, the rays of light acting upon the tobaccomight cause a further growth of the tobacco by utilizing the watersupply of the leaves and the food stored up therein. Vith the aid of theenzyms the starch content of the leaf is dissolved and the sugar whichis formed is sons, the cells would be prematurely killed before thestarch could be dissolved and the green color would thereby be set inthe leaf. If the coloring enzyms were still alive, they would act on thecell substance and produce colors showing over the green color of theleaf. It is desirable sometimes to hasten the starvation at the end ofthis period of'theprocess, in order to set some green color in the leafto produce a type of leaf having a greenish cast. The coloring enzymsact upon the cell substance and produce various final colors in the leafdepending upon the duration of the action, ,the amount of enzymspresent, and the amount of moisturestill retained by the cells, whichmoisture acts as a carrier. Y

Enzyms are destroyed by various influences among the most prominentbeing high temperatures,protoplasmic poisons or a surplusof moisture inthe leaf, which, if maintained for a period of time, causes, in'thelatter case, self-oxidation of the enzym. The

color producing. enzyms, if not prematurely destroyed, mix with thesoluble and oxidizable substance contained in the cell sap when thecells are killed, and can no longer hold the liquid contained therein.

In some types of tobacco a lemon yellow is desired, which requires thekilling ofthe enzyms directly after the yellow is developed. This iseffected'by rapidly drying out the leaf at a temperature high enough tokill the enzyms. In this type of tobacco the presence of, the coloringenz'yms is not es sehtial to the further treatment of the tobacco.'. Inother types of tobaccofparticu larly that which is used for cigars,enzyms are required for further treatment of the leaf and hence thetemperatures used in the curing must not be high enough to kill them.

In some ofthese types of tobacco,a light color is desired and thereforethe curing must be conducted in such a manner as to avoid darkening. Thetemperature necessary to effect the desired change will vary accordingto the types of tobacco being treated; for example, cigar wrapper type,cigar filler type, and bright tobacco type. In some types it isnecessary to kill the enzyms, but in other types they should not bekilled. In none of the ty es should there be applied a temperatureigh'enough to scorch the tobacco or to evaporate the essention oilscontained therein; in either of which cases, the tobacco would bepermanently injured; The highest temperature to be used in one type oftobacco might be 110 F., while in another type a temperature of 200 F.or over. might 'be desirable.

I-have referred to the desirable or necessary temperature as the optimumtemperature,

or a temperature not higher than the highest temperature that the typeof tobacco being treated will stand without damage. The

the maximum allowable or optimum temperature is reached can be easilydetected by those familiar withthe curing and treatment of tobacco.

' After the tobacco has been thoroughly For convenience in this secification and claims,

characteristics desired and the time when ing the curing, process aredependent upon the temperature used. The"excess'moisture of the leaf isliberated and must be carried away as the leaf is gradually starvedandchanges in-color.'

The principal object of my invention has been to provide a continuousmethod of treating tobacco, which shall be carried on in darkness, andunderconditions which may be absolutely governed, with respect totemperature and relative humidity, so that, not only thechemical changesgoing on in the leaf may be easily controlled, but the temperature andrelative humidity" may be varied to suit these changes, therebyproducing the desired properties in the leaf.

In carrying my invention into effect, the green leaves, after beingharvested, are suspended in any well known manner within a 7 suitablecuring apparatus, and subjected to the passage of continuouslycirculating air currents of a certain predetermined temperature andrelative humidity. The temperature of the air is then raised and itspercentage of relative humidity lowered until the tobacco has thedesired characteristics, whereupon the temperature of the air is lowered and its percentage of humidity raised, thus supplying sufficientmoisture to avoid breakage and for further treatment. 3

In practice, I prefer to use air at a temperature of to 90 F. and at arelatiye humidity of from 78% to 82%. The method is carried on underthese conditions for a length of time sufficient to consume the sur--plus food contained in the leaf and cause the death of the cells. Thetemperature of the treating air is then gradually raised to the optimumtemperature of the tobacco being treated, and the relative humidity isgradually lowered to about 65%. Tlfese conditions are maintained untilall parts of the toremoved from the apparatus it is subjected to aircurrents having a temperature of from bacco are fully cured. Before thetobacco is 70 to 85 F. and a relative humidity of from 80% to 85% forthe purpose of replacing the amount of moisture in the leaves necessaryfor its removal for storage or further treatment.

The limits of temperature and relative humidity are controlled by thetype of tobacco being treated,the stage 0 maturity in which it isharvested, and the'requirements of the finished tobacco.

The above method may be modified slightly by starting with a temperatureof from 70 to 80 F. and a relative humidity of 82% and graduallyincreasing the temperature and lowering the humidity, so that,

when the yellow color is reached, the tempera'ture will be between 90and 100 F. and the humidity about 78%. The temperature will becontinuously raised and the hu- -Then for the second part of thetreatment,

the temperature would be lowered to from 75 to 85 F. and the humidityincreased to from 80% to 85% for raising the moisture content to thenecessary point The last mentioned method is particularly adapted fortobacco which is used for cigar wrappers.

Having thus described my invention, what Iclaim'is:

1. A method of curing and treating to- .bacco which consists insubjecting it. to air currents having a temperature of from 70 to 90 F.and a relative humidity of from 78% to 82% for a suflicient length oftime' to consume the surplus food contained in the leaf and cause thedeath of the cells, then gradually raising the temperature of the aircurrents to a degree not higher than'the highest degree that the type oftobacco being treated will stand without damage, and gradually loweringthe relative humidity of the air currents to about 65%, until all partsof the tobacco are fully cured, and then gradually reducin thetemperature of the air currents to a ut 70 to 85 F. and graduallyincreasing the'relative humidity thereof to from 80% to 85%, for raisingthe moisture content to the necessa point.

2. A method ofcuring tobacco'whlch con-.

sists in subjecting it in darlmess to air currents having a temperatureof from 70 to 90 F. and arelative humidity of from 78% A to 82% for asuflicient length of time to consume the surplus food contained in theleaf and cause the death of the cells, then gradu-' ally raisingthetemperature of the air currents to a degree not higher than thehighest degree that the type of tobacco being treated will stand withoutdamage, and gradually lowering the relative humidity of the air currentsto about until all parts of the tobacco are fully cured;

3. A method of curingtobacco which consists in subjecting it to aircurrents having a temperature of from to 80F. and a relative humidity of82% for a suflicient length of time to consume the surplus 'foodcontained in the leaf and cause the death of the cells, then graduallyraising the temperature of the air currents to from 90 to 100 F. andgradually lowering the relative humidity of the air ,currents to 78%,and then continuously raising the temperature of the air currents to adegree not higher than the highest degree that the type 'of tobaccobeing treated will stand without damage, and

continuously lowering the relative humidity of the air currents to from65% to 70%, un-

til all parts of the tobacco have been fully cured.

4. A-method of curing and treating tobacco which consists in subjectingit to air currents having a temperature of from 70 to 80 F. andarelative humidity of 82% fora suflicient length of time to consume thesurplus food contained in the leaf and cause the death of the cells,then gradually raising the temperature of the air currents to from 90 to100 F and gradually lowering the relative humidity of the air currentsto 7 8%,

then continuously raising the temperature of the air currents to adegree not higher than the highest degree that the type of tobacco beingtreated'will stand without dam-- age, and continuously lowering therelative humidity of the air currents to from 65% to 70%, until allparts of the tobacco have been fully cured, and then gradually reducingthe temperature of the air currents to from to 85 F. and graduallyincreasing the relative humidity thereof to from to for ralsing themoisture content to the necessary point. 1

5. A method of curing tobacco which consists in subjecting it indarkness to air currentshaving a temperature of from 70 to 80 F. and arelative humidity of 82% for surplus'food contained in the leaf andcause the death of the cells, then gradually raising the temperature ofthe air currents to from to F. and gradually lowerin the relativehumidity of the air currents to 8%, and then continuously raising thetemperature of the air currents to a degree nothigher than the highestdegree that the type of tobacco being treated will stand without damage,and continuously lowering the relative humidity of the air currents tofrom 65% to 70%, until all parts of the tobacco have been fully cured.

In testimony whereof I have hereunto signed my name.

ALFRED CHARLES BUENSOD.

a sufficient length of time to consume the v

